The two are inexorably linked IMHO.
It sometimes takes you a while to recognize questionable data, and make the hard call to put it in the trashcan.
That said once you have good data much can be gleaned from it.
eg:
http://www.atscope.com.au/BRO/images/gx/centAdeep2.jpg
is the "deep" version of the same data here
http://www.atscope.com.au/BRO/gallery5.html